2D/3D numerical modelling of an underground longwall installation road

This paper presents a comprehensive numerical case study on the ground response and support performance for an underground coal mine longwall installation road. Coal mining installation roads represent high-risk excavations due to their large spans, which can lead to significant roof displacement. Three numerical modelling methodologies—FLAC2D, FLAC3D, and 3DEC—were employed to assess the ground behaviour and the effectiveness of ground support in mitigating such risks. These methods evaluated roof displacements, roadway convergence, and excavation damage zone characteristics. Models utilised the Generalized Hoek-Brown constitutive model in FLAC2D/3D to simulate the heterogeneous lithological units and anisotropic stress fields. Longitudinal Displacement Profiles (LDP) of the excavation were developed in FLAC3D, and Ground Reaction Curves (GRC) were extracted for both FLAC2D and 3DEC (quasi-3D only in this work) to determine the unsupported relaxation factor. A bonded block model (BBM) was incorporated in 3DEC to capture block-scale deformation. Model calibration and sensitivity analyses, including block size effects, were conducted to ensure reliable simulations. Results from the numerical analyses indicate that the designed support system is sufficient to control deformation, with the final roof-floor and rib-rib convergence remaining within acceptable limits (<2.5%). However, discrepancies between 3DEC and FLAC2D/3D were observed in roof displacements near the excavation surface, highlighting the influence of modelling methodology.